# [LeetCode] 71. Simplify Path

## Problem

Given an absolute path for a file (Unix-style), simplify it.

For example,

``````path = "/home/", => "/home"
path = "/a/./b/../../c/", => "/c"
path = "/a/../../b/../c//.//", => "/c"        //here: b is cancelled out, a is cancelled out
path = "/a//b////c/d//././/..", => "/a/b/c"   //here d is cancelled out
``````

In a UNIX-style file system, a period ('.') refers to the current directory, so it can be ignored in a simplified path. Additionally, a double period ("..") moves up a directory, so it cancels out whatever the last directory was. For more information, look here: https://en.wikipedia.org/wiki...

Corner Cases:

Did you consider the case where path = `"/../"`?
In this case, you should return `"/"`.
Another corner case is the path might contain multiple slashes '/' together, such as "/home//foo/".
In this case, you should ignore redundant slashes and return "/home/foo".

## Solution

``````class Solution {
public String simplifyPath(String path) {
Deque<String> stack = new ArrayDeque<>();
Set<String> ignore = new HashSet<>(Arrays.asList("", ".", ".."));
for (String dir: path.split("/")) {
if (!stack.isEmpty() && dir.equals("..")) stack.pop();
if (!ignore.contains(dir)) stack.push(dir);
}
String res = "";
while (!stack.isEmpty()) {
res = "/"+stack.pop()+res;
}
if (res.equals("")) return "/";
return res;
}
}``````